Applications of state space models in finance
Applications of state space models in finance
Applications of state space models in finance
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136 7 A Kalman filter based conditional multifactor pric<strong>in</strong>g model<br />
annually with the weight<strong>in</strong>gs be<strong>in</strong>g reviewed quarterly; see Stoxx Ltd. (2005) for more<br />
details.<br />
As the history <strong>of</strong> these two <strong>in</strong>dices only goes back to 30 June 1997, V GS is an assembled<br />
series: prior to <strong>in</strong>ception <strong>of</strong> the two DJ Stoxx style <strong>in</strong>dices, the value-growthspread<br />
is proxied by the difference between the log-returns <strong>of</strong> the Frank Russell 1000<br />
Value and the Frank Russell 1000 Growth <strong>in</strong>dex. Comparable to the DJ Stoxx style<br />
<strong>in</strong>dices for European stock markets, the objective <strong>of</strong> the two Frank Russell <strong>in</strong>dices is to<br />
give a comprehensive picture <strong>of</strong> value and growth stocks for a universe <strong>of</strong> the 1000 U.S.<br />
common stocks with the highest market capitalization. The style <strong>in</strong>dex membership is<br />
determ<strong>in</strong>ed by rank<strong>in</strong>g each stock <strong>in</strong> the Russell 1000 universe by their respective price<br />
to book ratio and their projected long-term growth. The <strong>in</strong>dices are reconstituted on a<br />
yearly basis; more details on the methodology are provided by Russell Investment Group<br />
(2007).<br />
Follow<strong>in</strong>g this procedure, the value and growth <strong>in</strong>dices, from which the time series<br />
<strong>of</strong> the V GS factor is derived, refer to different regions. However, dur<strong>in</strong>g the period for<br />
which weekly style returns are available for both European and U.S. markets, the correlation<br />
between the respective value (growth) returns is as high as 0.76 (0.73). Therefore,<br />
under the assumption that style performance <strong>in</strong> different regions — particularly <strong>in</strong> the<br />
U.S. and Europe — is highly correlated, the chosen procedure can be considered feasible.<br />
7.3.3 The market factor<br />
Given the importance <strong>of</strong> the market portfolio as a measure <strong>of</strong> aggregate wealth as <strong>in</strong>dicated<br />
by the CAPM (cf. ¢ 6), a market factor is typically <strong>in</strong>cluded as a central risk factor<br />
<strong>in</strong> the context <strong>of</strong> a multifactor pric<strong>in</strong>g model. Even though the goal <strong>of</strong> this chapter is<br />
to analyze the time-vary<strong>in</strong>g impact <strong>of</strong> macroeconomic and fundamental factors on European<br />
<strong>in</strong>dustry portfolios, the consideration <strong>of</strong> a non-macroeconomic, non-fundamental<br />
equity market factor is economically plausible: as stock prices respond very quickly to<br />
new <strong>in</strong>formation, aggregate market returns can be expected to reflect additional <strong>in</strong>formation<br />
that is not yet captured by the factors above (cf. Chen et al. 1986).<br />
As illustrated <strong>in</strong> Table 7.2, the excess log-returns <strong>of</strong> the DJ Stoxx Broad <strong>in</strong>dex, which<br />
serve as a proxy for the overall market throughout this thesis, are highly correlated with<br />
some <strong>of</strong> the chosen macroeconomic and fundamental risk factors. A common approach<br />
to assure that the set <strong>of</strong> considered risk factors is reasonably <strong>in</strong>dependent is to def<strong>in</strong>e a<br />
so-called residual market factor. This factor measures market returns after elim<strong>in</strong>at<strong>in</strong>g<br />
the effects <strong>of</strong> the macroeconomic and fundamental factors. Brennan et al. (2000), for<br />
example, regress the series <strong>of</strong> market returns on the set <strong>of</strong> the rema<strong>in</strong><strong>in</strong>g risk factors<br />
by us<strong>in</strong>g standard OLS. The obta<strong>in</strong>ed disturbance terms are then used as the residual<br />
market factor.<br />
As a means to avoid any look-ahead bias, <strong>in</strong> this chapter the residual benchmark factor,<br />
BMR, is derived as the series <strong>of</strong> one-step ahead prediction errors. These are obta<strong>in</strong>ed<br />
from an auxiliary regression with time-vary<strong>in</strong>g coefficients modeled as <strong>in</strong>dividual random<br />
¢<br />
walks (cf. 3.6.1.1). In order to use the Kalman filter for estimation purposes, the